Crinkling of the leaves can be caused by the overdose of certain growth regulators or fungicides or use of non-labeled materials on cucurbits.

Excessive green color of the foliage in addition to crinkling of leaves, and shortened internodes can be characteristic symptoms associated with these responses.

To the right is a plot with growth abnormality indicated by excessive green color foliage and to the left is a healthy watermelon foliage with normal green foliage color.